Two full decades have passed since David Letterman first brought his wacky late-night antics to CBS with "Late Show With David Letterman." To celebrate "Late Show's" 20th birthday, here are 20 slices of vintage Letterman that were so good, we didn't even mind feeling groggy the next day. — Dave Nemetz, Yahoo! TV

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Letterman Tisch

With CBS president and CEO Laurence Tisch at his side, talk-show host David Letterman gestures as he tells of his move from NBC to CBS during a news conference in New York, Jan. 14, 1993. CBS announced that Letterman's show will run against NBC's "The Tonight Show" with Jay Leno. (AP Photo/Alex Brandon)